Over the years, there has been developed a substantial body of patent and other literature directed to the formation and properties of poly(aryl ethers) (hereinafter called "PAE"). Some of the earliest work such as by Bonner, U.S. Pat. No. 3,065,205, involved the electrophilic aromatic substitution (e.g. Friedel-Crafts catalyzed) reaction of aromatic diacylhalides with unsubstituted aromatic compounds such as diphenyl ether. The evolution of this class to a much broader range of PAE's was achieved by Johnson et al., Journal of Polymer Science, A-1, vol. 5, 1967, pp. 2415-2427, Johnson et al., U.S. Pat. Nos. 4,108,837 and 4,175,175. Johnson et al. show that a very broad range of PAE can be formed by the nucleophilic aromatic substitution (condensation) reaction of an activated aromatic dihalide and an aromatic diol. By this method, Johnson et al. created a host of new PAE's including a broad class of poly(aryl ether ketones), hereinafter called "PAEK's".
In recent years, there has developed a growing interest in PAEKs as evidenced by Dahl, U.S. Pat. No. 3,953,400; Dahl et al., U.S. Pat. No. 3,956,240; Dahl, U.S. Pat. No. 4,247,682; Rose et al., U.S. Pat. No. 4,320,224; Maresca, U.S. Pat. No. 4,339,568; Atwood et al., Polymer, 1981, vol 22, August, pp. 1096-1103; Blundell et al., Polymer, 1983 vol. 24, August, pp. 953-958, Atwood et al., Polymer Preprints, 20, no. 1, April 1979, pp. 191-194; and Rueda et al., Polymer Communications, 1983, vol. 24, September, pp. 258-260. In early to mid-1970, Raychem Corp. commercially introduced a PAEK called STILAN.TM., a polymer whose acronym is PEK, each ether and keto group being separated by 1,4-phenylene units. In 1978, Imperial Chemical Industries PLC (ICI) commercialized a PAEK under the trademark Victrex PEEK. As PAEK is the acronym of poly(aryl ether ketone), PEEK is the acronym of poly(ether ether ketone) in which the 1,4-phenylene units in the structure are assumed.
Thus PAEKs are well known; they can be synthesized from a variety of starting materials; and they can be made with different melting temperatures and molecular weights. The PAEKs are crystalline, and as shown by the Dahl and Dahl et al. patents, supra, at sufficiently high molecular weights they can be tough, i.e., they exhibit high values (&gt;50 ft-lbs/in.sup.2) in the tensile impact test (ASTM D-1822). They have potential for a wide variety of uses, but because of the significant cost to manufacture them, they are expensive polymers. Their favorable properties class them in the upper bracket of engineering polymers.
PAEK's may be produced by the Friedel-Crafts catalyzed reaction of aromatic diacylhalides with unsubstituted aromatic compounds such as diphenyl ether as described in, for example, U.S. Pat. No. 3,065,205. These processes are generally inexpensive processes; however, the polymers produced by thse processes have been stated by Dahl et al., supra, to be brittle and thermally unstable. The Dahl patents, supra, allegedly depict more expensive processes for making superior PAEK's by Friedel-Crafts catalysis.
As indicated earlier PAEK's may also be produced by the nucleophilic route. The latter route is used, for example, for the commercial preparation of Victrex PEEK. The nucleophilic substitution reaction yields generally polymers with good properties. The main drawback of this type polymerization is the lack of solvents capable of dissolving the highly crystalline poly(aryl ether ketones) and keeping them in solution long enough to reach molecular weights sufficiently high at which satisfactory properties are displayed. The problem is particularly severe in cases wherein the preparation of higher melting materials (Tm&gt;350.degree. C.) is attempted by this route.